The goal of this project is to use neurobiological measures (in vivo 31P Magnetic Resonance Spectroscopy (MRS), Magnetic Resonance Imaging (MRI), and P300 evoked potentials), and neuropsychiatric assessment procedures to determine the effect of chronic alcohol abuse on the CNS morbidity of HIV infection. Our preliminary studies support an association between chronic alcohol abuse and greater HIV CNS morbidity. The alcohol abusing HIV+ patients in comparison to the non-alcohol-abusing HIV+ patients evidenced decreased 31P MRS brain high-energy phosphate metabolites and an increased latency of the frontal P3A component of the evoked potential. This project will attempt to replicate our initial results and to extend them by: (1) determining whether abstinence mitigates the alcohol abuse related increase in HIV CNS morbidity; (2) determining the effect of alcohol abuse and its cessation on the progression of CNS changes in HIV-infected individuals; (3) determining the degree to which changes in neuropsychiatric function over time are associated with changes in the neurobiological measures; and (4) using MR spectroscopic imaging (SI) to determine whether the HIV- related metabolic changes are due to focal lesions by correlating the locus and extent of MRI findings (e.g., brain atrophy and white matter disease) with the anatomic extent of MRS changes. In these studies, we will control for differences between the study samples in degree of systemic immune dysfunction, by studying HIV+ samples of (1) alcohol abusers, (2) non- alcohol-abusers, and (3) abstinent alcoholics that are comparably stratified with regard to CD4 percent.